I too am having fit content problems. Pref trashing did not help.

Trying to debug...

Any ideas welcome.

This is a bug or a big enough change in behavior that it should come with a warning alert the first time you use it. I've replicated it across different 8.0.1 installs and (Mac) OSs.

To replicate:

1. Place graphic. I haven't seen a difference among placed graphic types.
2. Resize the graphic frame non-proportionally.
3. Object=>Fitting=>Fit Content to Frame, so that the content is scaled non-proportionally. (Or select the content and scale it non-proportionally.)
4. Object=>Fitting=>Fit Content Proportionally. Nothing happens. (Or, if you scaled the content without fitting it in the previous step, the content may be centered, and it may be scaled, but the proportions won't be changed.)

I suppose you could make an argument that this is more correct than the old behavior—the command now means "Fit without changing the proportions"—but it's a big change, and I doubt anybody wants it to work this way.

Here's a short script that should more or less give the old behavior:

function fit(item) {
  var i, l, graphic;
  if (item instanceof Group) {
    for (i = 0, l = item.pageItems.length; i < l; i++) {
      fit(item.pageItems[i].getElements()[0]);
    }
  }
  else if (item.hasOwnProperty("imageTypeName")) {
    item.horizontalScale = item.horizontalScale < 0 ? -100 : 100;
    item.verticalScale = item.verticalScale < 0 ? -100 : 100;
    item.fit(FitOptions.PROPORTIONALLY);
  }
  else if (item.hasOwnProperty("graphics")) {
    for (i = 0, l = item.graphics.length; i < l; i++) {
      graphic = item.graphics[i];
      graphic.horizontalScale = graphic.horizontalScale < 0 ? -100 : 100;
      graphic.verticalScale = graphic.verticalScale < 0 ? -100 : 100;
      graphic.fit(FitOptions.PROPORTIONALLY);
    }
  }
}
function main() {
  var i, l;
  if (!app.documents.length) {
    return;
  }
  for (i = 0, l = app.selection.length; i < l; i++) {
    fit(app.selection[i]);
  }
}
app.doScript(main, ScriptLanguage.JAVASCRIPT, undefined, UndoModes.ENTIRE_SCRIPT, "Really Fit Content Proportionally");

There are  certainly some corner cases I've left out. Let me know if you try to use it and it doesn't work right.

Jeff

Did you try the script I posted?